tcp: fix stretch ACK bugs in Reno

Change Reno to properly handle stretch ACKs in additive increase mode by passing in the count of ACKed packets to tcp_cong_avoid_ai(). In addition, if snd_cwnd crosses snd_ssthresh during slow start processing, and we then exit slow start mode, we need to carry over any remaining "credit" for packets ACKed and apply that to additive increase by passing this remaining "acked" count to tcp_cong_avoid_ai(). Reported-by: Eyal Perry <[email protected]> Signed-off-by: Neal Cardwell <[email protected]> Signed-off-by: Yuchung Cheng <[email protected]> Signed-off-by: Eric Dumazet <[email protected]> Signed-off-by: David S. Miller <[email protected]>
kawasaki · Jan 29, 2015 · c22bdca · c22bdca
1 parent 814d488
commit c22bdca
Showing 1 changed file with 6 additions and 4 deletions.
diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c
@@ -335,11 +335,13 @@ void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 acked)
 		return;
 
 	/* In "safe" area, increase. */
-	if (tp->snd_cwnd <= tp->snd_ssthresh)
-		tcp_slow_start(tp, acked);
+	if (tp->snd_cwnd <= tp->snd_ssthresh) {
+		acked = tcp_slow_start(tp, acked);
+		if (!acked)
+			return;
+	}
 	/* In dangerous area, increase slowly. */
-	else
-		tcp_cong_avoid_ai(tp, tp->snd_cwnd, 1);
+	tcp_cong_avoid_ai(tp, tp->snd_cwnd, acked);
 }
 EXPORT_SYMBOL_GPL(tcp_reno_cong_avoid);